The Activating Effect of Strong Acid for Pd-Catalyzed Directed C–H Activation by Concerted Metalation-Deprotonation Mechanism

Abstract

A computational study on the origin of the activating effect for Pd-catalyzed directed C–H activation by the concerted metalation-deprotonation (CMD) mechanism is conducted. DFT calculations indicate that strong acids can make Pd catalysts coordinate with directing groups (DGs) of the substrates more strongly and lower the C–H activation energy barrier. For the CMD mechanism, the electrophilicity of the Pd center and the basicity of the corresponding acid ligand for deprotonating the C–H bond are vital to the overall C–H activation energy barrier. Furthermore, this rule might disclose the role of some additives for C–H activation.

Palladium Catalysis: Dependence of the Efficiency of C−C Bond Formation on Carboxylate Ligand and Alkali Metal Carboxylate or Carboxylic Acid Additive. Part A: the C(sp2)−C(sp2), C(sp2)−C(sp3) and C(sp3)−C(sp3) Bonds

“…. [47] Subsequently, Tsuji, Fujihara and co-workers performed a similar annelation using catalytic PdCl 2 and two sets of experimental conditions, which mainly led to similar results (Scheme 6d). [41] The very bulky tri(cyclohexylmethyl)acetic acid gave the best yields while 3-(adamantan-2-yl)-2,2dimethylpropanoic acid was much less efficient.…”

Direct Arylation Polycondensation of Thiophene‐Based C−H Monomers†

“…Notably, carboxylate can also influence the electrophilicity of the Pd center. [ 42 ] The factors of Δ E dist and Δ E int are usually contradictory. The presence of electron‐donating groups leads to a more negative Δ E int but increases the Δ E dist , and vice versa.…”